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Diffstat (limited to 'src/libs/3rdparty/lua/src/lgc.c')
| -rw-r--r-- | src/libs/3rdparty/lua/src/lgc.c | 1739 |
1 files changed, 1739 insertions, 0 deletions
diff --git a/src/libs/3rdparty/lua/src/lgc.c b/src/libs/3rdparty/lua/src/lgc.c new file mode 100644 index 0000000000..a3094ff571 --- /dev/null +++ b/src/libs/3rdparty/lua/src/lgc.c @@ -0,0 +1,1739 @@ +/* +** $Id: lgc.c $ +** Garbage Collector +** See Copyright Notice in lua.h +*/ + +#define lgc_c +#define LUA_CORE + +#include "lprefix.h" + +#include <stdio.h> +#include <string.h> + + +#include "lua.h" + +#include "ldebug.h" +#include "ldo.h" +#include "lfunc.h" +#include "lgc.h" +#include "lmem.h" +#include "lobject.h" +#include "lstate.h" +#include "lstring.h" +#include "ltable.h" +#include "ltm.h" + + +/* +** Maximum number of elements to sweep in each single step. +** (Large enough to dissipate fixed overheads but small enough +** to allow small steps for the collector.) +*/ +#define GCSWEEPMAX 100 + +/* +** Maximum number of finalizers to call in each single step. +*/ +#define GCFINMAX 10 + + +/* +** Cost of calling one finalizer. +*/ +#define GCFINALIZECOST 50 + + +/* +** The equivalent, in bytes, of one unit of "work" (visiting a slot, +** sweeping an object, etc.) +*/ +#define WORK2MEM sizeof(TValue) + + +/* +** macro to adjust 'pause': 'pause' is actually used like +** 'pause / PAUSEADJ' (value chosen by tests) +*/ +#define PAUSEADJ 100 + + +/* mask with all color bits */ +#define maskcolors (bitmask(BLACKBIT) | WHITEBITS) + +/* mask with all GC bits */ +#define maskgcbits (maskcolors | AGEBITS) + + +/* macro to erase all color bits then set only the current white bit */ +#define makewhite(g,x) \ + (x->marked = cast_byte((x->marked & ~maskcolors) | luaC_white(g))) + +/* make an object gray (neither white nor black) */ +#define set2gray(x) resetbits(x->marked, maskcolors) + + +/* make an object black (coming from any color) */ +#define set2black(x) \ + (x->marked = cast_byte((x->marked & ~WHITEBITS) | bitmask(BLACKBIT))) + + +#define valiswhite(x) (iscollectable(x) && iswhite(gcvalue(x))) + +#define keyiswhite(n) (keyiscollectable(n) && iswhite(gckey(n))) + + +/* +** Protected access to objects in values +*/ +#define gcvalueN(o) (iscollectable(o) ? gcvalue(o) : NULL) + + +#define markvalue(g,o) { checkliveness(g->mainthread,o); \ + if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); } + +#define markkey(g, n) { if keyiswhite(n) reallymarkobject(g,gckey(n)); } + +#define markobject(g,t) { if (iswhite(t)) reallymarkobject(g, obj2gco(t)); } + +/* +** mark an object that can be NULL (either because it is really optional, +** or it was stripped as debug info, or inside an uncompleted structure) +*/ +#define markobjectN(g,t) { if (t) markobject(g,t); } + +static void reallymarkobject (global_State *g, GCObject *o); +static lu_mem atomic (lua_State *L); +static void entersweep (lua_State *L); + + +/* +** {====================================================== +** Generic functions +** ======================================================= +*/ + + +/* +** one after last element in a hash array +*/ +#define gnodelast(h) gnode(h, cast_sizet(sizenode(h))) + + +static GCObject **getgclist (GCObject *o) { + switch (o->tt) { + case LUA_VTABLE: return &gco2t(o)->gclist; + case LUA_VLCL: return &gco2lcl(o)->gclist; + case LUA_VCCL: return &gco2ccl(o)->gclist; + case LUA_VTHREAD: return &gco2th(o)->gclist; + case LUA_VPROTO: return &gco2p(o)->gclist; + case LUA_VUSERDATA: { + Udata *u = gco2u(o); + lua_assert(u->nuvalue > 0); + return &u->gclist; + } + default: lua_assert(0); return 0; + } +} + + +/* +** Link a collectable object 'o' with a known type into the list 'p'. +** (Must be a macro to access the 'gclist' field in different types.) +*/ +#define linkgclist(o,p) linkgclist_(obj2gco(o), &(o)->gclist, &(p)) + +static void linkgclist_ (GCObject *o, GCObject **pnext, GCObject **list) { + lua_assert(!isgray(o)); /* cannot be in a gray list */ + *pnext = *list; + *list = o; + set2gray(o); /* now it is */ +} + + +/* +** Link a generic collectable object 'o' into the list 'p'. +*/ +#define linkobjgclist(o,p) linkgclist_(obj2gco(o), getgclist(o), &(p)) + + + +/* +** Clear keys for empty entries in tables. If entry is empty, mark its +** entry as dead. This allows the collection of the key, but keeps its +** entry in the table: its removal could break a chain and could break +** a table traversal. Other places never manipulate dead keys, because +** its associated empty value is enough to signal that the entry is +** logically empty. +*/ +static void clearkey (Node *n) { + lua_assert(isempty(gval(n))); + if (keyiscollectable(n)) + setdeadkey(n); /* unused key; remove it */ +} + + +/* +** tells whether a key or value can be cleared from a weak +** table. Non-collectable objects are never removed from weak +** tables. Strings behave as 'values', so are never removed too. for +** other objects: if really collected, cannot keep them; for objects +** being finalized, keep them in keys, but not in values +*/ +static int iscleared (global_State *g, const GCObject *o) { + if (o == NULL) return 0; /* non-collectable value */ + else if (novariant(o->tt) == LUA_TSTRING) { + markobject(g, o); /* strings are 'values', so are never weak */ + return 0; + } + else return iswhite(o); +} + + +/* +** Barrier that moves collector forward, that is, marks the white object +** 'v' being pointed by the black object 'o'. In the generational +** mode, 'v' must also become old, if 'o' is old; however, it cannot +** be changed directly to OLD, because it may still point to non-old +** objects. So, it is marked as OLD0. In the next cycle it will become +** OLD1, and in the next it will finally become OLD (regular old). By +** then, any object it points to will also be old. If called in the +** incremental sweep phase, it clears the black object to white (sweep +** it) to avoid other barrier calls for this same object. (That cannot +** be done is generational mode, as its sweep does not distinguish +** whites from deads.) +*/ +void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) { + global_State *g = G(L); + lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o)); + if (keepinvariant(g)) { /* must keep invariant? */ + reallymarkobject(g, v); /* restore invariant */ + if (isold(o)) { + lua_assert(!isold(v)); /* white object could not be old */ + setage(v, G_OLD0); /* restore generational invariant */ + } + } + else { /* sweep phase */ + lua_assert(issweepphase(g)); + if (g->gckind == KGC_INC) /* incremental mode? */ + makewhite(g, o); /* mark 'o' as white to avoid other barriers */ + } +} + + +/* +** barrier that moves collector backward, that is, mark the black object +** pointing to a white object as gray again. +*/ +void luaC_barrierback_ (lua_State *L, GCObject *o) { + global_State *g = G(L); + lua_assert(isblack(o) && !isdead(g, o)); + lua_assert((g->gckind == KGC_GEN) == (isold(o) && getage(o) != G_TOUCHED1)); + if (getage(o) == G_TOUCHED2) /* already in gray list? */ + set2gray(o); /* make it gray to become touched1 */ + else /* link it in 'grayagain' and paint it gray */ + linkobjgclist(o, g->grayagain); + if (isold(o)) /* generational mode? */ + setage(o, G_TOUCHED1); /* touched in current cycle */ +} + + +void luaC_fix (lua_State *L, GCObject *o) { + global_State *g = G(L); + lua_assert(g->allgc == o); /* object must be 1st in 'allgc' list! */ + set2gray(o); /* they will be gray forever */ + setage(o, G_OLD); /* and old forever */ + g->allgc = o->next; /* remove object from 'allgc' list */ + o->next = g->fixedgc; /* link it to 'fixedgc' list */ + g->fixedgc = o; +} + + +/* +** create a new collectable object (with given type, size, and offset) +** and link it to 'allgc' list. +*/ +GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz, size_t offset) { + global_State *g = G(L); + char *p = cast_charp(luaM_newobject(L, novariant(tt), sz)); + GCObject *o = cast(GCObject *, p + offset); + o->marked = luaC_white(g); + o->tt = tt; + o->next = g->allgc; + g->allgc = o; + return o; +} + + +GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) { + return luaC_newobjdt(L, tt, sz, 0); +} + +/* }====================================================== */ + + + +/* +** {====================================================== +** Mark functions +** ======================================================= +*/ + + +/* +** Mark an object. Userdata with no user values, strings, and closed +** upvalues are visited and turned black here. Open upvalues are +** already indirectly linked through their respective threads in the +** 'twups' list, so they don't go to the gray list; nevertheless, they +** are kept gray to avoid barriers, as their values will be revisited +** by the thread or by 'remarkupvals'. Other objects are added to the +** gray list to be visited (and turned black) later. Both userdata and +** upvalues can call this function recursively, but this recursion goes +** for at most two levels: An upvalue cannot refer to another upvalue +** (only closures can), and a userdata's metatable must be a table. +*/ +static void reallymarkobject (global_State *g, GCObject *o) { + switch (o->tt) { + case LUA_VSHRSTR: + case LUA_VLNGSTR: { + set2black(o); /* nothing to visit */ + break; + } + case LUA_VUPVAL: { + UpVal *uv = gco2upv(o); + if (upisopen(uv)) + set2gray(uv); /* open upvalues are kept gray */ + else + set2black(uv); /* closed upvalues are visited here */ + markvalue(g, uv->v.p); /* mark its content */ + break; + } + case LUA_VUSERDATA: { + Udata *u = gco2u(o); + if (u->nuvalue == 0) { /* no user values? */ + markobjectN(g, u->metatable); /* mark its metatable */ + set2black(u); /* nothing else to mark */ + break; + } + /* else... */ + } /* FALLTHROUGH */ + case LUA_VLCL: case LUA_VCCL: case LUA_VTABLE: + case LUA_VTHREAD: case LUA_VPROTO: { + linkobjgclist(o, g->gray); /* to be visited later */ + break; + } + default: lua_assert(0); break; + } +} + + +/* +** mark metamethods for basic types +*/ +static void markmt (global_State *g) { + int i; + for (i=0; i < LUA_NUMTAGS; i++) + markobjectN(g, g->mt[i]); +} + + +/* +** mark all objects in list of being-finalized +*/ +static lu_mem markbeingfnz (global_State *g) { + GCObject *o; + lu_mem count = 0; + for (o = g->tobefnz; o != NULL; o = o->next) { + count++; + markobject(g, o); + } + return count; +} + + +/* +** For each non-marked thread, simulates a barrier between each open +** upvalue and its value. (If the thread is collected, the value will be +** assigned to the upvalue, but then it can be too late for the barrier +** to act. The "barrier" does not need to check colors: A non-marked +** thread must be young; upvalues cannot be older than their threads; so +** any visited upvalue must be young too.) Also removes the thread from +** the list, as it was already visited. Removes also threads with no +** upvalues, as they have nothing to be checked. (If the thread gets an +** upvalue later, it will be linked in the list again.) +*/ +static int remarkupvals (global_State *g) { + lua_State *thread; + lua_State **p = &g->twups; + int work = 0; /* estimate of how much work was done here */ + while ((thread = *p) != NULL) { + work++; + if (!iswhite(thread) && thread->openupval != NULL) + p = &thread->twups; /* keep marked thread with upvalues in the list */ + else { /* thread is not marked or without upvalues */ + UpVal *uv; + lua_assert(!isold(thread) || thread->openupval == NULL); + *p = thread->twups; /* remove thread from the list */ + thread->twups = thread; /* mark that it is out of list */ + for (uv = thread->openupval; uv != NULL; uv = uv->u.open.next) { + lua_assert(getage(uv) <= getage(thread)); + work++; + if (!iswhite(uv)) { /* upvalue already visited? */ + lua_assert(upisopen(uv) && isgray(uv)); + markvalue(g, uv->v.p); /* mark its value */ + } + } + } + } + return work; +} + + +static void cleargraylists (global_State *g) { + g->gray = g->grayagain = NULL; + g->weak = g->allweak = g->ephemeron = NULL; +} + + +/* +** mark root set and reset all gray lists, to start a new collection +*/ +static void restartcollection (global_State *g) { + cleargraylists(g); + markobject(g, g->mainthread); + markvalue(g, &g->l_registry); + markmt(g); + markbeingfnz(g); /* mark any finalizing object left from previous cycle */ +} + +/* }====================================================== */ + + +/* +** {====================================================== +** Traverse functions +** ======================================================= +*/ + + +/* +** Check whether object 'o' should be kept in the 'grayagain' list for +** post-processing by 'correctgraylist'. (It could put all old objects +** in the list and leave all the work to 'correctgraylist', but it is +** more efficient to avoid adding elements that will be removed.) Only +** TOUCHED1 objects need to be in the list. TOUCHED2 doesn't need to go +** back to a gray list, but then it must become OLD. (That is what +** 'correctgraylist' does when it finds a TOUCHED2 object.) +*/ +static void genlink (global_State *g, GCObject *o) { + lua_assert(isblack(o)); + if (getage(o) == G_TOUCHED1) { /* touched in this cycle? */ + linkobjgclist(o, g->grayagain); /* link it back in 'grayagain' */ + } /* everything else do not need to be linked back */ + else if (getage(o) == G_TOUCHED2) + changeage(o, G_TOUCHED2, G_OLD); /* advance age */ +} + + +/* +** Traverse a table with weak values and link it to proper list. During +** propagate phase, keep it in 'grayagain' list, to be revisited in the +** atomic phase. In the atomic phase, if table has any white value, +** put it in 'weak' list, to be cleared. +*/ +static void traverseweakvalue (global_State *g, Table *h) { + Node *n, *limit = gnodelast(h); + /* if there is array part, assume it may have white values (it is not + worth traversing it now just to check) */ + int hasclears = (h->alimit > 0); + for (n = gnode(h, 0); n < limit; n++) { /* traverse hash part */ + if (isempty(gval(n))) /* entry is empty? */ + clearkey(n); /* clear its key */ + else { + lua_assert(!keyisnil(n)); + markkey(g, n); + if (!hasclears && iscleared(g, gcvalueN(gval(n)))) /* a white value? */ + hasclears = 1; /* table will have to be cleared */ + } + } + if (g->gcstate == GCSatomic && hasclears) + linkgclist(h, g->weak); /* has to be cleared later */ + else + linkgclist(h, g->grayagain); /* must retraverse it in atomic phase */ +} + + +/* +** Traverse an ephemeron table and link it to proper list. Returns true +** iff any object was marked during this traversal (which implies that +** convergence has to continue). During propagation phase, keep table +** in 'grayagain' list, to be visited again in the atomic phase. In +** the atomic phase, if table has any white->white entry, it has to +** be revisited during ephemeron convergence (as that key may turn +** black). Otherwise, if it has any white key, table has to be cleared +** (in the atomic phase). In generational mode, some tables +** must be kept in some gray list for post-processing; this is done +** by 'genlink'. +*/ +static int traverseephemeron (global_State *g, Table *h, int inv) { + int marked = 0; /* true if an object is marked in this traversal */ + int hasclears = 0; /* true if table has white keys */ + int hasww = 0; /* true if table has entry "white-key -> white-value" */ + unsigned int i; + unsigned int asize = luaH_realasize(h); + unsigned int nsize = sizenode(h); + /* traverse array part */ + for (i = 0; i < asize; i++) { + if (valiswhite(&h->array[i])) { + marked = 1; + reallymarkobject(g, gcvalue(&h->array[i])); + } + } + /* traverse hash part; if 'inv', traverse descending + (see 'convergeephemerons') */ + for (i = 0; i < nsize; i++) { + Node *n = inv ? gnode(h, nsize - 1 - i) : gnode(h, i); + if (isempty(gval(n))) /* entry is empty? */ + clearkey(n); /* clear its key */ + else if (iscleared(g, gckeyN(n))) { /* key is not marked (yet)? */ + hasclears = 1; /* table must be cleared */ + if (valiswhite(gval(n))) /* value not marked yet? */ + hasww = 1; /* white-white entry */ + } + else if (valiswhite(gval(n))) { /* value not marked yet? */ + marked = 1; + reallymarkobject(g, gcvalue(gval(n))); /* mark it now */ + } + } + /* link table into proper list */ + if (g->gcstate == GCSpropagate) + linkgclist(h, g->grayagain); /* must retraverse it in atomic phase */ + else if (hasww) /* table has white->white entries? */ + linkgclist(h, g->ephemeron); /* have to propagate again */ + else if (hasclears) /* table has white keys? */ + linkgclist(h, g->allweak); /* may have to clean white keys */ + else + genlink(g, obj2gco(h)); /* check whether collector still needs to see it */ + return marked; +} + + +static void traversestrongtable (global_State *g, Table *h) { + Node *n, *limit = gnodelast(h); + unsigned int i; + unsigned int asize = luaH_realasize(h); + for (i = 0; i < asize; i++) /* traverse array part */ + markvalue(g, &h->array[i]); + for (n = gnode(h, 0); n < limit; n++) { /* traverse hash part */ + if (isempty(gval(n))) /* entry is empty? */ + clearkey(n); /* clear its key */ + else { + lua_assert(!keyisnil(n)); + markkey(g, n); + markvalue(g, gval(n)); + } + } + genlink(g, obj2gco(h)); +} + + +static lu_mem traversetable (global_State *g, Table *h) { + const char *weakkey, *weakvalue; + const TValue *mode = gfasttm(g, h->metatable, TM_MODE); + markobjectN(g, h->metatable); + if (mode && ttisstring(mode) && /* is there a weak mode? */ + (cast_void(weakkey = strchr(svalue(mode), 'k')), + cast_void(weakvalue = strchr(svalue(mode), 'v')), + (weakkey || weakvalue))) { /* is really weak? */ + if (!weakkey) /* strong keys? */ + traverseweakvalue(g, h); + else if (!weakvalue) /* strong values? */ + traverseephemeron(g, h, 0); + else /* all weak */ + linkgclist(h, g->allweak); /* nothing to traverse now */ + } + else /* not weak */ + traversestrongtable(g, h); + return 1 + h->alimit + 2 * allocsizenode(h); +} + + +static int traverseudata (global_State *g, Udata *u) { + int i; + markobjectN(g, u->metatable); /* mark its metatable */ + for (i = 0; i < u->nuvalue; i++) + markvalue(g, &u->uv[i].uv); + genlink(g, obj2gco(u)); + return 1 + u->nuvalue; +} + + +/* +** Traverse a prototype. (While a prototype is being build, its +** arrays can be larger than needed; the extra slots are filled with +** NULL, so the use of 'markobjectN') +*/ +static int traverseproto (global_State *g, Proto *f) { + int i; + markobjectN(g, f->source); + for (i = 0; i < f->sizek; i++) /* mark literals */ + markvalue(g, &f->k[i]); + for (i = 0; i < f->sizeupvalues; i++) /* mark upvalue names */ + markobjectN(g, f->upvalues[i].name); + for (i = 0; i < f->sizep; i++) /* mark nested protos */ + markobjectN(g, f->p[i]); + for (i = 0; i < f->sizelocvars; i++) /* mark local-variable names */ + markobjectN(g, f->locvars[i].varname); + return 1 + f->sizek + f->sizeupvalues + f->sizep + f->sizelocvars; +} + + +static int traverseCclosure (global_State *g, CClosure *cl) { + int i; + for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */ + markvalue(g, &cl->upvalue[i]); + return 1 + cl->nupvalues; +} + +/* +** Traverse a Lua closure, marking its prototype and its upvalues. +** (Both can be NULL while closure is being created.) +*/ +static int traverseLclosure (global_State *g, LClosure *cl) { + int i; + markobjectN(g, cl->p); /* mark its prototype */ + for (i = 0; i < cl->nupvalues; i++) { /* visit its upvalues */ + UpVal *uv = cl->upvals[i]; + markobjectN(g, uv); /* mark upvalue */ + } + return 1 + cl->nupvalues; +} + + +/* +** Traverse a thread, marking the elements in the stack up to its top +** and cleaning the rest of the stack in the final traversal. That +** ensures that the entire stack have valid (non-dead) objects. +** Threads have no barriers. In gen. mode, old threads must be visited +** at every cycle, because they might point to young objects. In inc. +** mode, the thread can still be modified before the end of the cycle, +** and therefore it must be visited again in the atomic phase. To ensure +** these visits, threads must return to a gray list if they are not new +** (which can only happen in generational mode) or if the traverse is in +** the propagate phase (which can only happen in incremental mode). +*/ +static int traversethread (global_State *g, lua_State *th) { + UpVal *uv; + StkId o = th->stack.p; + if (isold(th) || g->gcstate == GCSpropagate) + linkgclist(th, g->grayagain); /* insert into 'grayagain' list */ + if (o == NULL) + return 1; /* stack not completely built yet */ + lua_assert(g->gcstate == GCSatomic || + th->openupval == NULL || isintwups(th)); + for (; o < th->top.p; o++) /* mark live elements in the stack */ + markvalue(g, s2v(o)); + for (uv = th->openupval; uv != NULL; uv = uv->u.open.next) + markobject(g, uv); /* open upvalues cannot be collected */ + if (g->gcstate == GCSatomic) { /* final traversal? */ + for (; o < th->stack_last.p + EXTRA_STACK; o++) + setnilvalue(s2v(o)); /* clear dead stack slice */ + /* 'remarkupvals' may have removed thread from 'twups' list */ + if (!isintwups(th) && th->openupval != NULL) { + th->twups = g->twups; /* link it back to the list */ + g->twups = th; + } + } + else if (!g->gcemergency) + luaD_shrinkstack(th); /* do not change stack in emergency cycle */ + return 1 + stacksize(th); +} + + +/* +** traverse one gray object, turning it to black. +*/ +static lu_mem propagatemark (global_State *g) { + GCObject *o = g->gray; + nw2black(o); + g->gray = *getgclist(o); /* remove from 'gray' list */ + switch (o->tt) { + case LUA_VTABLE: return traversetable(g, gco2t(o)); + case LUA_VUSERDATA: return traverseudata(g, gco2u(o)); + case LUA_VLCL: return traverseLclosure(g, gco2lcl(o)); + case LUA_VCCL: return traverseCclosure(g, gco2ccl(o)); + case LUA_VPROTO: return traverseproto(g, gco2p(o)); + case LUA_VTHREAD: return traversethread(g, gco2th(o)); + default: lua_assert(0); return 0; + } +} + + +static lu_mem propagateall (global_State *g) { + lu_mem tot = 0; + while (g->gray) + tot += propagatemark(g); + return tot; +} + + +/* +** Traverse all ephemeron tables propagating marks from keys to values. +** Repeat until it converges, that is, nothing new is marked. 'dir' +** inverts the direction of the traversals, trying to speed up +** convergence on chains in the same table. +** +*/ +static void convergeephemerons (global_State *g) { + int changed; + int dir = 0; + do { + GCObject *w; + GCObject *next = g->ephemeron; /* get ephemeron list */ + g->ephemeron = NULL; /* tables may return to this list when traversed */ + changed = 0; + while ((w = next) != NULL) { /* for each ephemeron table */ + Table *h = gco2t(w); + next = h->gclist; /* list is rebuilt during loop */ + nw2black(h); /* out of the list (for now) */ + if (traverseephemeron(g, h, dir)) { /* marked some value? */ + propagateall(g); /* propagate changes */ + changed = 1; /* will have to revisit all ephemeron tables */ + } + } + dir = !dir; /* invert direction next time */ + } while (changed); /* repeat until no more changes */ +} + +/* }====================================================== */ + + +/* +** {====================================================== +** Sweep Functions +** ======================================================= +*/ + + +/* +** clear entries with unmarked keys from all weaktables in list 'l' +*/ +static void clearbykeys (global_State *g, GCObject *l) { + for (; l; l = gco2t(l)->gclist) { + Table *h = gco2t(l); + Node *limit = gnodelast(h); + Node *n; + for (n = gnode(h, 0); n < limit; n++) { + if (iscleared(g, gckeyN(n))) /* unmarked key? */ + setempty(gval(n)); /* remove entry */ + if (isempty(gval(n))) /* is entry empty? */ + clearkey(n); /* clear its key */ + } + } +} + + +/* +** clear entries with unmarked values from all weaktables in list 'l' up +** to element 'f' +*/ +static void clearbyvalues (global_State *g, GCObject *l, GCObject *f) { + for (; l != f; l = gco2t(l)->gclist) { + Table *h = gco2t(l); + Node *n, *limit = gnodelast(h); + unsigned int i; + unsigned int asize = luaH_realasize(h); + for (i = 0; i < asize; i++) { + TValue *o = &h->array[i]; + if (iscleared(g, gcvalueN(o))) /* value was collected? */ + setempty(o); /* remove entry */ + } + for (n = gnode(h, 0); n < limit; n++) { + if (iscleared(g, gcvalueN(gval(n)))) /* unmarked value? */ + setempty(gval(n)); /* remove entry */ + if (isempty(gval(n))) /* is entry empty? */ + clearkey(n); /* clear its key */ + } + } +} + + +static void freeupval (lua_State *L, UpVal *uv) { + if (upisopen(uv)) + luaF_unlinkupval(uv); + luaM_free(L, uv); +} + + +static void freeobj (lua_State *L, GCObject *o) { + switch (o->tt) { + case LUA_VPROTO: + luaF_freeproto(L, gco2p(o)); + break; + case LUA_VUPVAL: + freeupval(L, gco2upv(o)); + break; + case LUA_VLCL: { + LClosure *cl = gco2lcl(o); + luaM_freemem(L, cl, sizeLclosure(cl->nupvalues)); + break; + } + case LUA_VCCL: { + CClosure *cl = gco2ccl(o); + luaM_freemem(L, cl, sizeCclosure(cl->nupvalues)); + break; + } + case LUA_VTABLE: + luaH_free(L, gco2t(o)); + break; + case LUA_VTHREAD: + luaE_freethread(L, gco2th(o)); + break; + case LUA_VUSERDATA: { + Udata *u = gco2u(o); + luaM_freemem(L, o, sizeudata(u->nuvalue, u->len)); + break; + } + case LUA_VSHRSTR: { + TString *ts = gco2ts(o); + luaS_remove(L, ts); /* remove it from hash table */ + luaM_freemem(L, ts, sizelstring(ts->shrlen)); + break; + } + case LUA_VLNGSTR: { + TString *ts = gco2ts(o); + luaM_freemem(L, ts, sizelstring(ts->u.lnglen)); + break; + } + default: lua_assert(0); + } +} + + +/* +** sweep at most 'countin' elements from a list of GCObjects erasing dead +** objects, where a dead object is one marked with the old (non current) +** white; change all non-dead objects back to white, preparing for next +** collection cycle. Return where to continue the traversal or NULL if +** list is finished. ('*countout' gets the number of elements traversed.) +*/ +static GCObject **sweeplist (lua_State *L, GCObject **p, int countin, + int *countout) { + global_State *g = G(L); + int ow = otherwhite(g); + int i; + int white = luaC_white(g); /* current white */ + for (i = 0; *p != NULL && i < countin; i++) { + GCObject *curr = *p; + int marked = curr->marked; + if (isdeadm(ow, marked)) { /* is 'curr' dead? */ + *p = curr->next; /* remove 'curr' from list */ + freeobj(L, curr); /* erase 'curr' */ + } + else { /* change mark to 'white' */ + curr->marked = cast_byte((marked & ~maskgcbits) | white); + p = &curr->next; /* go to next element */ + } + } + if (countout) + *countout = i; /* number of elements traversed */ + return (*p == NULL) ? NULL : p; +} + + +/* +** sweep a list until a live object (or end of list) +*/ +static GCObject **sweeptolive (lua_State *L, GCObject **p) { + GCObject **old = p; + do { + p = sweeplist(L, p, 1, NULL); + } while (p == old); + return p; +} + +/* }====================================================== */ + + +/* +** {====================================================== +** Finalization +** ======================================================= +*/ + +/* +** If possible, shrink string table. +*/ +static void checkSizes (lua_State *L, global_State *g) { + if (!g->gcemergency) { + if (g->strt.nuse < g->strt.size / 4) { /* string table too big? */ + l_mem olddebt = g->GCdebt; + luaS_resize(L, g->strt.size / 2); + g->GCestimate += g->GCdebt - olddebt; /* correct estimate */ + } + } +} + + +/* +** Get the next udata to be finalized from the 'tobefnz' list, and +** link it back into the 'allgc' list. +*/ +static GCObject *udata2finalize (global_State *g) { + GCObject *o = g->tobefnz; /* get first element */ + lua_assert(tofinalize(o)); + g->tobefnz = o->next; /* remove it from 'tobefnz' list */ + o->next = g->allgc; /* return it to 'allgc' list */ + g->allgc = o; + resetbit(o->marked, FINALIZEDBIT); /* object is "normal" again */ + if (issweepphase(g)) + makewhite(g, o); /* "sweep" object */ + else if (getage(o) == G_OLD1) + g->firstold1 = o; /* it is the first OLD1 object in the list */ + return o; +} + + +static void dothecall (lua_State *L, void *ud) { + UNUSED(ud); + luaD_callnoyield(L, L->top.p - 2, 0); +} + + +static void GCTM (lua_State *L) { + global_State *g = G(L); + const TValue *tm; + TValue v; + lua_assert(!g->gcemergency); + setgcovalue(L, &v, udata2finalize(g)); + tm = luaT_gettmbyobj(L, &v, TM_GC); + if (!notm(tm)) { /* is there a finalizer? */ + int status; + lu_byte oldah = L->allowhook; + int oldgcstp = g->gcstp; + g->gcstp |= GCSTPGC; /* avoid GC steps */ + L->allowhook = 0; /* stop debug hooks during GC metamethod */ + setobj2s(L, L->top.p++, tm); /* push finalizer... */ + setobj2s(L, L->top.p++, &v); /* ... and its argument */ + L->ci->callstatus |= CIST_FIN; /* will run a finalizer */ + status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top.p - 2), 0); + L->ci->callstatus &= ~CIST_FIN; /* not running a finalizer anymore */ + L->allowhook = oldah; /* restore hooks */ + g->gcstp = oldgcstp; /* restore state */ + if (l_unlikely(status != LUA_OK)) { /* error while running __gc? */ + luaE_warnerror(L, "__gc"); + L->top.p--; /* pops error object */ + } + } +} + + +/* +** Call a few finalizers +*/ +static int runafewfinalizers (lua_State *L, int n) { + global_State *g = G(L); + int i; + for (i = 0; i < n && g->tobefnz; i++) + GCTM(L); /* call one finalizer */ + return i; +} + + +/* +** call all pending finalizers +*/ +static void callallpendingfinalizers (lua_State *L) { + global_State *g = G(L); + while (g->tobefnz) + GCTM(L); +} + + +/* +** find last 'next' field in list 'p' list (to add elements in its end) +*/ +static GCObject **findlast (GCObject **p) { + while (*p != NULL) + p = &(*p)->next; + return p; +} + + +/* +** Move all unreachable objects (or 'all' objects) that need +** finalization from list 'finobj' to list 'tobefnz' (to be finalized). +** (Note that objects after 'finobjold1' cannot be white, so they +** don't need to be traversed. In incremental mode, 'finobjold1' is NULL, +** so the whole list is traversed.) +*/ +static void separatetobefnz (global_State *g, int all) { + GCObject *curr; + GCObject **p = &g->finobj; + GCObject **lastnext = findlast(&g->tobefnz); + while ((curr = *p) != g->finobjold1) { /* traverse all finalizable objects */ + lua_assert(tofinalize(curr)); + if (!(iswhite(curr) || all)) /* not being collected? */ + p = &curr->next; /* don't bother with it */ + else { + if (curr == g->finobjsur) /* removing 'finobjsur'? */ + g->finobjsur = curr->next; /* correct it */ + *p = curr->next; /* remove 'curr' from 'finobj' list */ + curr->next = *lastnext; /* link at the end of 'tobefnz' list */ + *lastnext = curr; + lastnext = &curr->next; + } + } +} + + +/* +** If pointer 'p' points to 'o', move it to the next element. +*/ +static void checkpointer (GCObject **p, GCObject *o) { + if (o == *p) + *p = o->next; +} + + +/* +** Correct pointers to objects inside 'allgc' list when +** object 'o' is being removed from the list. +*/ +static void correctpointers (global_State *g, GCObject *o) { + checkpointer(&g->survival, o); + checkpointer(&g->old1, o); + checkpointer(&g->reallyold, o); + checkpointer(&g->firstold1, o); +} + + +/* +** if object 'o' has a finalizer, remove it from 'allgc' list (must +** search the list to find it) and link it in 'finobj' list. +*/ +void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) { + global_State *g = G(L); + if (tofinalize(o) || /* obj. is already marked... */ + gfasttm(g, mt, TM_GC) == NULL || /* or has no finalizer... */ + (g->gcstp & GCSTPCLS)) /* or closing state? */ + return; /* nothing to be done */ + else { /* move 'o' to 'finobj' list */ + GCObject **p; + if (issweepphase(g)) { + makewhite(g, o); /* "sweep" object 'o' */ + if (g->sweepgc == &o->next) /* should not remove 'sweepgc' object */ + g->sweepgc = sweeptolive(L, g->sweepgc); /* change 'sweepgc' */ + } + else + correctpointers(g, o); + /* search for pointer pointing to 'o' */ + for (p = &g->allgc; *p != o; p = &(*p)->next) { /* empty */ } + *p = o->next; /* remove 'o' from 'allgc' list */ + o->next = g->finobj; /* link it in 'finobj' list */ + g->finobj = o; + l_setbit(o->marked, FINALIZEDBIT); /* mark it as such */ + } +} + +/* }====================================================== */ + + +/* +** {====================================================== +** Generational Collector +** ======================================================= +*/ + + +/* +** Set the "time" to wait before starting a new GC cycle; cycle will +** start when memory use hits the threshold of ('estimate' * pause / +** PAUSEADJ). (Division by 'estimate' should be OK: it cannot be zero, +** because Lua cannot even start with less than PAUSEADJ bytes). +*/ +static void setpause (global_State *g) { + l_mem threshold, debt; + int pause = getgcparam(g->gcpause); + l_mem estimate = g->GCestimate / PAUSEADJ; /* adjust 'estimate' */ + lua_assert(estimate > 0); + threshold = (pause < MAX_LMEM / estimate) /* overflow? */ + ? estimate * pause /* no overflow */ + : MAX_LMEM; /* overflow; truncate to maximum */ + debt = gettotalbytes(g) - threshold; + if (debt > 0) debt = 0; + luaE_setdebt(g, debt); +} + + +/* +** Sweep a list of objects to enter generational mode. Deletes dead +** objects and turns the non dead to old. All non-dead threads---which +** are now old---must be in a gray list. Everything else is not in a +** gray list. Open upvalues are also kept gray. +*/ +static void sweep2old (lua_State *L, GCObject **p) { + GCObject *curr; + global_State *g = G(L); + while ((curr = *p) != NULL) { + if (iswhite(curr)) { /* is 'curr' dead? */ + lua_assert(isdead(g, curr)); + *p = curr->next; /* remove 'curr' from list */ + freeobj(L, curr); /* erase 'curr' */ + } + else { /* all surviving objects become old */ + setage(curr, G_OLD); + if (curr->tt == LUA_VTHREAD) { /* threads must be watched */ + lua_State *th = gco2th(curr); + linkgclist(th, g->grayagain); /* insert into 'grayagain' list */ + } + else if (curr->tt == LUA_VUPVAL && upisopen(gco2upv(curr))) + set2gray(curr); /* open upvalues are always gray */ + else /* everything else is black */ + nw2black(curr); + p = &curr->next; /* go to next element */ + } + } +} + + +/* +** Sweep for generational mode. Delete dead objects. (Because the +** collection is not incremental, there are no "new white" objects +** during the sweep. So, any white object must be dead.) For +** non-dead objects, advance their ages and clear the color of +** new objects. (Old objects keep their colors.) +** The ages of G_TOUCHED1 and G_TOUCHED2 objects cannot be advanced +** here, because these old-generation objects are usually not swept +** here. They will all be advanced in 'correctgraylist'. That function +** will also remove objects turned white here from any gray list. +*/ +static GCObject **sweepgen (lua_State *L, global_State *g, GCObject **p, + GCObject *limit, GCObject **pfirstold1) { + static const lu_byte nextage[] = { + G_SURVIVAL, /* from G_NEW */ + G_OLD1, /* from G_SURVIVAL */ + G_OLD1, /* from G_OLD0 */ + G_OLD, /* from G_OLD1 */ + G_OLD, /* from G_OLD (do not change) */ + G_TOUCHED1, /* from G_TOUCHED1 (do not change) */ + G_TOUCHED2 /* from G_TOUCHED2 (do not change) */ + }; + int white = luaC_white(g); + GCObject *curr; + while ((curr = *p) != limit) { + if (iswhite(curr)) { /* is 'curr' dead? */ + lua_assert(!isold(curr) && isdead(g, curr)); + *p = curr->next; /* remove 'curr' from list */ + freeobj(L, curr); /* erase 'curr' */ + } + else { /* correct mark and age */ + if (getage(curr) == G_NEW) { /* new objects go back to white */ + int marked = curr->marked & ~maskgcbits; /* erase GC bits */ + curr->marked = cast_byte(marked | G_SURVIVAL | white); + } + else { /* all other objects will be old, and so keep their color */ + setage(curr, nextage[getage(curr)]); + if (getage(curr) == G_OLD1 && *pfirstold1 == NULL) + *pfirstold1 = curr; /* first OLD1 object in the list */ + } + p = &curr->next; /* go to next element */ + } + } + return p; +} + + +/* +** Traverse a list making all its elements white and clearing their +** age. In incremental mode, all objects are 'new' all the time, +** except for fixed strings (which are always old). +*/ +static void whitelist (global_State *g, GCObject *p) { + int white = luaC_white(g); + for (; p != NULL; p = p->next) + p->marked = cast_byte((p->marked & ~maskgcbits) | white); +} + + +/* +** Correct a list of gray objects. Return pointer to where rest of the +** list should be linked. +** Because this correction is done after sweeping, young objects might +** be turned white and still be in the list. They are only removed. +** 'TOUCHED1' objects are advanced to 'TOUCHED2' and remain on the list; +** Non-white threads also remain on the list; 'TOUCHED2' objects become +** regular old; they and anything else are removed from the list. +*/ +static GCObject **correctgraylist (GCObject **p) { + GCObject *curr; + while ((curr = *p) != NULL) { + GCObject **next = getgclist(curr); + if (iswhite(curr)) + goto remove; /* remove all white objects */ + else if (getage(curr) == G_TOUCHED1) { /* touched in this cycle? */ + lua_assert(isgray(curr)); + nw2black(curr); /* make it black, for next barrier */ + changeage(curr, G_TOUCHED1, G_TOUCHED2); + goto remain; /* keep it in the list and go to next element */ + } + else if (curr->tt == LUA_VTHREAD) { + lua_assert(isgray(curr)); + goto remain; /* keep non-white threads on the list */ + } + else { /* everything else is removed */ + lua_assert(isold(curr)); /* young objects should be white here */ + if (getage(curr) == G_TOUCHED2) /* advance from TOUCHED2... */ + changeage(curr, G_TOUCHED2, G_OLD); /* ... to OLD */ + nw2black(curr); /* make object black (to be removed) */ + goto remove; + } + remove: *p = *next; continue; + remain: p = next; continue; + } + return p; +} + + +/* +** Correct all gray lists, coalescing them into 'grayagain'. +*/ +static void correctgraylists (global_State *g) { + GCObject **list = correctgraylist(&g->grayagain); + *list = g->weak; g->weak = NULL; + list = correctgraylist(list); + *list = g->allweak; g->allweak = NULL; + list = correctgraylist(list); + *list = g->ephemeron; g->ephemeron = NULL; + correctgraylist(list); +} + + +/* +** Mark black 'OLD1' objects when starting a new young collection. +** Gray objects are already in some gray list, and so will be visited +** in the atomic step. +*/ +static void markold (global_State *g, GCObject *from, GCObject *to) { + GCObject *p; + for (p = from; p != to; p = p->next) { + if (getage(p) == G_OLD1) { + lua_assert(!iswhite(p)); + changeage(p, G_OLD1, G_OLD); /* now they are old */ + if (isblack(p)) + reallymarkobject(g, p); + } + } +} + + +/* +** Finish a young-generation collection. +*/ +static void finishgencycle (lua_State *L, global_State *g) { + correctgraylists(g); + checkSizes(L, g); + g->gcstate = GCSpropagate; /* skip restart */ + if (!g->gcemergency) + callallpendingfinalizers(L); +} + + +/* +** Does a young collection. First, mark 'OLD1' objects. Then does the +** atomic step. Then, sweep all lists and advance pointers. Finally, +** finish the collection. +*/ +static void youngcollection (lua_State *L, global_State *g) { + GCObject **psurvival; /* to point to first non-dead survival object */ + GCObject *dummy; /* dummy out parameter to 'sweepgen' */ + lua_assert(g->gcstate == GCSpropagate); + if (g->firstold1) { /* are there regular OLD1 objects? */ + markold(g, g->firstold1, g->reallyold); /* mark them */ + g->firstold1 = NULL; /* no more OLD1 objects (for now) */ + } + markold(g, g->finobj, g->finobjrold); + markold(g, g->tobefnz, NULL); + atomic(L); + + /* sweep nursery and get a pointer to its last live element */ + g->gcstate = GCSswpallgc; + psurvival = sweepgen(L, g, &g->allgc, g->survival, &g->firstold1); + /* sweep 'survival' */ + sweepgen(L, g, psurvival, g->old1, &g->firstold1); + g->reallyold = g->old1; + g->old1 = *psurvival; /* 'survival' survivals are old now */ + g->survival = g->allgc; /* all news are survivals */ + + /* repeat for 'finobj' lists */ + dummy = NULL; /* no 'firstold1' optimization for 'finobj' lists */ + psurvival = sweepgen(L, g, &g->finobj, g->finobjsur, &dummy); + /* sweep 'survival' */ + sweepgen(L, g, psurvival, g->finobjold1, &dummy); + g->finobjrold = g->finobjold1; + g->finobjold1 = *psurvival; /* 'survival' survivals are old now */ + g->finobjsur = g->finobj; /* all news are survivals */ + + sweepgen(L, g, &g->tobefnz, NULL, &dummy); + finishgencycle(L, g); +} + + +/* +** Clears all gray lists, sweeps objects, and prepare sublists to enter +** generational mode. The sweeps remove dead objects and turn all +** surviving objects to old. Threads go back to 'grayagain'; everything +** else is turned black (not in any gray list). +*/ +static void atomic2gen (lua_State *L, global_State *g) { + cleargraylists(g); + /* sweep all elements making them old */ + g->gcstate = GCSswpallgc; + sweep2old(L, &g->allgc); + /* everything alive now is old */ + g->reallyold = g->old1 = g->survival = g->allgc; + g->firstold1 = NULL; /* there are no OLD1 objects anywhere */ + + /* repeat for 'finobj' lists */ + sweep2old(L, &g->finobj); + g->finobjrold = g->finobjold1 = g->finobjsur = g->finobj; + + sweep2old(L, &g->tobefnz); + + g->gckind = KGC_GEN; + g->lastatomic = 0; + g->GCestimate = gettotalbytes(g); /* base for memory control */ + finishgencycle(L, g); +} + + +/* +** Set debt for the next minor collection, which will happen when +** memory grows 'genminormul'%. +*/ +static void setminordebt (global_State *g) { + luaE_setdebt(g, -(cast(l_mem, (gettotalbytes(g) / 100)) * g->genminormul)); +} + + +/* +** Enter generational mode. Must go until the end of an atomic cycle +** to ensure that all objects are correctly marked and weak tables +** are cleared. Then, turn all objects into old and finishes the +** collection. +*/ +static lu_mem entergen (lua_State *L, global_State *g) { + lu_mem numobjs; + luaC_runtilstate(L, bitmask(GCSpause)); /* prepare to start a new cycle */ + luaC_runtilstate(L, bitmask(GCSpropagate)); /* start new cycle */ + numobjs = atomic(L); /* propagates all and then do the atomic stuff */ + atomic2gen(L, g); + setminordebt(g); /* set debt assuming next cycle will be minor */ + return numobjs; +} + + +/* +** Enter incremental mode. Turn all objects white, make all +** intermediate lists point to NULL (to avoid invalid pointers), +** and go to the pause state. +*/ +static void enterinc (global_State *g) { + whitelist(g, g->allgc); + g->reallyold = g->old1 = g->survival = NULL; + whitelist(g, g->finobj); + whitelist(g, g->tobefnz); + g->finobjrold = g->finobjold1 = g->finobjsur = NULL; + g->gcstate = GCSpause; + g->gckind = KGC_INC; + g->lastatomic = 0; +} + + +/* +** Change collector mode to 'newmode'. +*/ +void luaC_changemode (lua_State *L, int newmode) { + global_State *g = G(L); + if (newmode != g->gckind) { + if (newmode == KGC_GEN) /* entering generational mode? */ + entergen(L, g); + else + enterinc(g); /* entering incremental mode */ + } + g->lastatomic = 0; +} + + +/* +** Does a full collection in generational mode. +*/ +static lu_mem fullgen (lua_State *L, global_State *g) { + enterinc(g); + return entergen(L, g); +} + + +/* +** Does a major collection after last collection was a "bad collection". +** +** When the program is building a big structure, it allocates lots of +** memory but generates very little garbage. In those scenarios, +** the generational mode just wastes time doing small collections, and +** major collections are frequently what we call a "bad collection", a +** collection that frees too few objects. To avoid the cost of switching +** between generational mode and the incremental mode needed for full +** (major) collections, the collector tries to stay in incremental mode +** after a bad collection, and to switch back to generational mode only +** after a "good" collection (one that traverses less than 9/8 objects +** of the previous one). +** The collector must choose whether to stay in incremental mode or to +** switch back to generational mode before sweeping. At this point, it +** does not know the real memory in use, so it cannot use memory to +** decide whether to return to generational mode. Instead, it uses the +** number of objects traversed (returned by 'atomic') as a proxy. The +** field 'g->lastatomic' keeps this count from the last collection. +** ('g->lastatomic != 0' also means that the last collection was bad.) +*/ +static void stepgenfull (lua_State *L, global_State *g) { + lu_mem newatomic; /* count of traversed objects */ + lu_mem lastatomic = g->lastatomic; /* count from last collection */ + if (g->gckind == KGC_GEN) /* still in generational mode? */ + enterinc(g); /* enter incremental mode */ + luaC_runtilstate(L, bitmask(GCSpropagate)); /* start new cycle */ + newatomic = atomic(L); /* mark everybody */ + if (newatomic < lastatomic + (lastatomic >> 3)) { /* good collection? */ + atomic2gen(L, g); /* return to generational mode */ + setminordebt(g); + } + else { /* another bad collection; stay in incremental mode */ + g->GCestimate = gettotalbytes(g); /* first estimate */; + entersweep(L); + luaC_runtilstate(L, bitmask(GCSpause)); /* finish collection */ + setpause(g); + g->lastatomic = newatomic; + } +} + + +/* +** Does a generational "step". +** Usually, this means doing a minor collection and setting the debt to +** make another collection when memory grows 'genminormul'% larger. +** +** However, there are exceptions. If memory grows 'genmajormul'% +** larger than it was at the end of the last major collection (kept +** in 'g->GCestimate'), the function does a major collection. At the +** end, it checks whether the major collection was able to free a +** decent amount of memory (at least half the growth in memory since +** previous major collection). If so, the collector keeps its state, +** and the next collection will probably be minor again. Otherwise, +** we have what we call a "bad collection". In that case, set the field +** 'g->lastatomic' to signal that fact, so that the next collection will +** go to 'stepgenfull'. +** +** 'GCdebt <= 0' means an explicit call to GC step with "size" zero; +** in that case, do a minor collection. +*/ +static void genstep (lua_State *L, global_State *g) { + if (g->lastatomic != 0) /* last collection was a bad one? */ + stepgenfull(L, g); /* do a full step */ + else { + lu_mem majorbase = g->GCestimate; /* memory after last major collection */ + lu_mem majorinc = (majorbase / 100) * getgcparam(g->genmajormul); + if (g->GCdebt > 0 && gettotalbytes(g) > majorbase + majorinc) { + lu_mem numobjs = fullgen(L, g); /* do a major collection */ + if (gettotalbytes(g) < majorbase + (majorinc / 2)) { + /* collected at least half of memory growth since last major + collection; keep doing minor collections. */ + lua_assert(g->lastatomic == 0); + } + else { /* bad collection */ + g->lastatomic = numobjs; /* signal that last collection was bad */ + setpause(g); /* do a long wait for next (major) collection */ + } + } + else { /* regular case; do a minor collection */ + youngcollection(L, g); + setminordebt(g); + g->GCestimate = majorbase; /* preserve base value */ + } + } + lua_assert(isdecGCmodegen(g)); +} + +/* }====================================================== */ + + +/* +** {====================================================== +** GC control +** ======================================================= +*/ + + +/* +** Enter first sweep phase. +** The call to 'sweeptolive' makes the pointer point to an object +** inside the list (instead of to the header), so that the real sweep do +** not need to skip objects created between "now" and the start of the +** real sweep. +*/ +static void entersweep (lua_State *L) { + global_State *g = G(L); + g->gcstate = GCSswpallgc; + lua_assert(g->sweepgc == NULL); + g->sweepgc = sweeptolive(L, &g->allgc); +} + + +/* +** Delete all objects in list 'p' until (but not including) object +** 'limit'. +*/ +static void deletelist (lua_State *L, GCObject *p, GCObject *limit) { + while (p != limit) { + GCObject *next = p->next; + freeobj(L, p); + p = next; + } +} + + +/* +** Call all finalizers of the objects in the given Lua state, and +** then free all objects, except for the main thread. +*/ +void luaC_freeallobjects (lua_State *L) { + global_State *g = G(L); + g->gcstp = GCSTPCLS; /* no extra finalizers after here */ + luaC_changemode(L, KGC_INC); + separatetobefnz(g, 1); /* separate all objects with finalizers */ + lua_assert(g->finobj == NULL); + callallpendingfinalizers(L); + deletelist(L, g->allgc, obj2gco(g->mainthread)); + lua_assert(g->finobj == NULL); /* no new finalizers */ + deletelist(L, g->fixedgc, NULL); /* collect fixed objects */ + lua_assert(g->strt.nuse == 0); +} + + +static lu_mem atomic (lua_State *L) { + global_State *g = G(L); + lu_mem work = 0; + GCObject *origweak, *origall; + GCObject *grayagain = g->grayagain; /* save original list */ + g->grayagain = NULL; + lua_assert(g->ephemeron == NULL && g->weak == NULL); + lua_assert(!iswhite(g->mainthread)); + g->gcstate = GCSatomic; + markobject(g, L); /* mark running thread */ + /* registry and global metatables may be changed by API */ + markvalue(g, &g->l_registry); + markmt(g); /* mark global metatables */ + work += propagateall(g); /* empties 'gray' list */ + /* remark occasional upvalues of (maybe) dead threads */ + work += remarkupvals(g); + work += propagateall(g); /* propagate changes */ + g->gray = grayagain; + work += propagateall(g); /* traverse 'grayagain' list */ + convergeephemerons(g); + /* at this point, all strongly accessible objects are marked. */ + /* Clear values from weak tables, before checking finalizers */ + clearbyvalues(g, g->weak, NULL); + clearbyvalues(g, g->allweak, NULL); + origweak = g->weak; origall = g->allweak; + separatetobefnz(g, 0); /* separate objects to be finalized */ + work += markbeingfnz(g); /* mark objects that will be finalized */ + work += propagateall(g); /* remark, to propagate 'resurrection' */ + convergeephemerons(g); + /* at this point, all resurrected objects are marked. */ + /* remove dead objects from weak tables */ + clearbykeys(g, g->ephemeron); /* clear keys from all ephemeron tables */ + clearbykeys(g, g->allweak); /* clear keys from all 'allweak' tables */ + /* clear values from resurrected weak tables */ + clearbyvalues(g, g->weak, origweak); + clearbyvalues(g, g->allweak, origall); + luaS_clearcache(g); + g->currentwhite = cast_byte(otherwhite(g)); /* flip current white */ + lua_assert(g->gray == NULL); + return work; /* estimate of slots marked by 'atomic' */ +} + + +static int sweepstep (lua_State *L, global_State *g, + int nextstate, GCObject **nextlist) { + if (g->sweepgc) { + l_mem olddebt = g->GCdebt; + int count; + g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX, &count); + g->GCestimate += g->GCdebt - olddebt; /* update estimate */ + return count; + } + else { /* enter next state */ + g->gcstate = nextstate; + g->sweepgc = nextlist; + return 0; /* no work done */ + } +} + + +static lu_mem singlestep (lua_State *L) { + global_State *g = G(L); + lu_mem work; + lua_assert(!g->gcstopem); /* collector is not reentrant */ + g->gcstopem = 1; /* no emergency collections while collecting */ + switch (g->gcstate) { + case GCSpause: { + restartcollection(g); + g->gcstate = GCSpropagate; + work = 1; + break; + } + case GCSpropagate: { + if (g->gray == NULL) { /* no more gray objects? */ + g->gcstate = GCSenteratomic; /* finish propagate phase */ + work = 0; + } + else + work = propagatemark(g); /* traverse one gray object */ + break; + } + case GCSenteratomic: { + work = atomic(L); /* work is what was traversed by 'atomic' */ + entersweep(L); + g->GCestimate = gettotalbytes(g); /* first estimate */; + break; + } + case GCSswpallgc: { /* sweep "regular" objects */ + work = sweepstep(L, g, GCSswpfinobj, &g->finobj); + break; + } + case GCSswpfinobj: { /* sweep objects with finalizers */ + work = sweepstep(L, g, GCSswptobefnz, &g->tobefnz); + break; + } + case GCSswptobefnz: { /* sweep objects to be finalized */ + work = sweepstep(L, g, GCSswpend, NULL); + break; + } + case GCSswpend: { /* finish sweeps */ + checkSizes(L, g); + g->gcstate = GCScallfin; + work = 0; + break; + } + case GCScallfin: { /* call remaining finalizers */ + if (g->tobefnz && !g->gcemergency) { + g->gcstopem = 0; /* ok collections during finalizers */ + work = runafewfinalizers(L, GCFINMAX) * GCFINALIZECOST; + } + else { /* emergency mode or no more finalizers */ + g->gcstate = GCSpause; /* finish collection */ + work = 0; + } + break; + } + default: lua_assert(0); return 0; + } + g->gcstopem = 0; + return work; +} + + +/* +** advances the garbage collector until it reaches a state allowed +** by 'statemask' +*/ +void luaC_runtilstate (lua_State *L, int statesmask) { + global_State *g = G(L); + while (!testbit(statesmask, g->gcstate)) + singlestep(L); +} + + + +/* +** Performs a basic incremental step. The debt and step size are +** converted from bytes to "units of work"; then the function loops +** running single steps until adding that many units of work or +** finishing a cycle (pause state). Finally, it sets the debt that +** controls when next step will be performed. +*/ +static void incstep (lua_State *L, global_State *g) { + int stepmul = (getgcparam(g->gcstepmul) | 1); /* avoid division by 0 */ + l_mem debt = (g->GCdebt / WORK2MEM) * stepmul; + l_mem stepsize = (g->gcstepsize <= log2maxs(l_mem)) + ? ((cast(l_mem, 1) << g->gcstepsize) / WORK2MEM) * stepmul + : MAX_LMEM; /* overflow; keep maximum value */ + do { /* repeat until pause or enough "credit" (negative debt) */ + lu_mem work = singlestep(L); /* perform one single step */ + debt -= work; + } while (debt > -stepsize && g->gcstate != GCSpause); + if (g->gcstate == GCSpause) + setpause(g); /* pause until next cycle */ + else { + debt = (debt / stepmul) * WORK2MEM; /* convert 'work units' to bytes */ + luaE_setdebt(g, debt); + } +} + +/* +** Performs a basic GC step if collector is running. (If collector is +** not running, set a reasonable debt to avoid it being called at +** every single check.) +*/ +void luaC_step (lua_State *L) { + global_State *g = G(L); + if (!gcrunning(g)) /* not running? */ + luaE_setdebt(g, -2000); + else { + if(isdecGCmodegen(g)) + genstep(L, g); + else + incstep(L, g); + } +} + + +/* +** Perform a full collection in incremental mode. +** Before running the collection, check 'keepinvariant'; if it is true, +** there may be some objects marked as black, so the collector has +** to sweep all objects to turn them back to white (as white has not +** changed, nothing will be collected). +*/ +static void fullinc (lua_State *L, global_State *g) { + if (keepinvariant(g)) /* black objects? */ + entersweep(L); /* sweep everything to turn them back to white */ + /* finish any pending sweep phase to start a new cycle */ + luaC_runtilstate(L, bitmask(GCSpause)); + luaC_runtilstate(L, bitmask(GCScallfin)); /* run up to finalizers */ + /* estimate must be correct after a full GC cycle */ + lua_assert(g->GCestimate == gettotalbytes(g)); + luaC_runtilstate(L, bitmask(GCSpause)); /* finish collection */ + setpause(g); +} + + +/* +** Performs a full GC cycle; if 'isemergency', set a flag to avoid +** some operations which could change the interpreter state in some +** unexpected ways (running finalizers and shrinking some structures). +*/ +void luaC_fullgc (lua_State *L, int isemergency) { + global_State *g = G(L); + lua_assert(!g->gcemergency); + g->gcemergency = isemergency; /* set flag */ + if (g->gckind == KGC_INC) + fullinc(L, g); + else + fullgen(L, g); + g->gcemergency = 0; +} + +/* }====================================================== */ + + |